Kingdom: Animalia
Phylum: Chordata
Class: Osteichthyes
Order: Perciformes
Family: Coryphaenidae
Genus: Coryphaena
Species: Coryphaena hippurus
Description of Species
Dolphinfish are compressed, elongated fish with a large mouth and many fine teeth. They have a long dorsal fin that stretches from their nape to a forked tail. The anal fin is also long, extending from mid-body to their forked tail. Males have a bony crest on the head that is not present in females. These colorful fish exhibit hues of gold on the sides, iridescent blues and greens on the sides and backs, and white and yellow underneath. The average size of the mature dolphinfish is between 1.5 - 3 ft. and weighs 15 - 30 lbs. Males are generally heavier than females regardless of length (Palko et al. 1982). The largest fish ever recorded was an 87 lb. fish caught off the coast of Costa Rica. Studies of sex ratios are inconclusive in regards to the distribution of males and females worldwide (Palko et al. 1982).
Habitat
Coryphaena hippurus is a pelagic fish that inhabits tropical and sub-tropical oceans worldwide. This cosmopolitan saltwater fish prefers water above 70 degrees F. (McClane 1974), and therefore, temperature determines the range for this species. The dolphinfish inhabits open waters near the edges of the continental shelves in tropical and sub-tropical environments (Palko et al. 1982). Vertical distribution in the ocean ranges from the surface to approximately 90 feet underwater (Palko et al. 1982). They are commonly found loitering near objects floating in water that may harbor prey species. These objects can be as substantial as large clumps of Sargassum weed, and insignificant as small streams of sea foam. Not much is known about the migration patterns of this fish, but it has been hypothesized that they follow seasonal fluctuations in water temperature in search of more productive food sources (Palko et al. 1982).
Natural History
Dolphinfish are migratory fish that travel in schools known as pods. The size of these schools is usually determined by size or sex. Young female dolphinfish tend to congregate near Sargassum patties while the young males usually seek the company of older males and females in the open ocean (Palko et al. 1982). Additionally, larger fish travel in smaller pods. Research concerning migration has provided little information about what determines the movements of dolphinfish. Some of the migration hypotheses that have been introduced include the migration of dolphinfish as part of a pre-spawning event, migration correlating with the drift of Sargassum, and migration in pursuit of new sources of food.
Dolphinfish are voracious predators. In addition to their favorite prey, flying-fish, numerous other ocean species have been found in their stomachs. These species include fish, squid, shrimp, crustaceans, and even small dolphinfish (Bannister 1976). Much of the food eaten by dolphinfish is located near clumps of Sargassum and other floating objects. Food is detected using keen eyesight (Kelly and Kira 1997) and statoacoustic organs (Palko et al. 1982).
The insatiable appetite of dolphinfish may be connected to their high metabolism and tremendous growth rate. It is estimated that dolphinfish grow 1 - 1.5 ft./year (Palko et al. 1982). Their high metabolic rate has been attributed to physiological adaptations that conform to the lifestyle of a fast-moving pelagic predator (Benetti et al. 1995). Dolphinfish reach sexual maturity in one year, and typically live a maximum of four years (Palko et al. 1982). Studies have shown that a predominant number of dolphinfish populations are comprised of fish younger than two years-old (Palko et al. 1982).
Although they are almost at the top of the food web, dolphinfish are prey for a number of predators. Dolphinfish have been found in the stomachs of a variety of tuna and marlin species.
The Coryphaenidae family consists of two species in one genera. The genus Coryphaena is composed of the dolphinfish (C. hippurus) and the pompano dolphin (C. esquelis). Both of these species are similar in size and appearance, but differ in the amount and shape of fin rays, number of vertebrae, size and shape of tooth patches, and the coloration of juvenile fish (Palko et. al 1982).
The order Perciformes, of which the Coryphaenidae family is a member, belongs to the class Osteichthyes. This class, also known as Teleosts, or Bony Fish, is further divided into a subclass known as Actinopterygii. Members of the Actinopterygii subclass had its origins 225-280 million years ago during Permian times (Greenwood 1963). These species were an known as the Semionotiformes (Greenwood 1963). During the Triassic period, the Semionotiformes evolved into the Pholidophoriformes order (Greenwood 1963). The Pholidophoriformes existed during the Triassic and Jurassic periods, after which time they became extinct, but not before giving rise to another order, the Leptolepiformes (Greenwood 1963). The Leptolepiformes were the first members of the Actinopyerygii subclass with a homocercal tail (Greenwood 1963). This order is credited with evolving into the Clupeiformes during the Cretaceous period (Greenwood 1963). Throughout the Cretaceous, continued evolution spawned the Beryciformes, and finally, the present-day order of which the Coryphaenidae family is a member, Perciformes (Greenwood 1963).
Despite being located in the Perciformes order, their is some debate about the classification of the Coryphaendidae family (Nelson 1994). The family is monogeneric and similarities to the percoid fishes is currently unclear (Palko et al. 1982). Furthermore, it has been suggested that Coryphaenidae is a sister to the Rachycentridae and Echeneidae families, and together, they form a monophyletic group (Nelson 1994).
Distribution
Dolphinfish have been found as far north as Georges Bank, Nova Scotia in the western Atlantic, and as far south as Rio De Janeiro, Brazil (Palko et al. 1982). They are abundant in the Gulf of Mexico, off the North Carolina coast, in the Florida Current, off Central America, and throughout the Caribbean Sea.
In the eastern Atlantic, the dolphinfish is found between the Bay of Biscay off the coast of France, and has reportedly been detected as far south as South Africa (Palko et al. 1982). Dolphinfish inhabit the Mediterranean Sea, and are frequently found around the Madeira and Balearic Islands off the coast of Spain.
Dolphinfish in the western Pacific are distributed from Japan in the north, to New Zealand in the south (Palko et al. 1982). They are frequently found off the Philippines Islands and Taiwan.
In the eastern Pacific, dolphinfish have been encountered from the Oregon coast to the offshore waters of Peru (Palko et al. 1982). They are prevalent in the Gulf of California, Panama Bay, and Peruvian waters.
Dolphinfish have been collected off the coasts of Kenya and Tanzania, and are known to exist throughout the northern and central Indian Ocean (Palko et al. 1982).
Economic Uses
In addition to predation by marlin and tuna species, dolphinfish are also sought after by human cultures because of their firm meat and delicate flavor. Dolphinfish support commercial and sportfishing industries worldwide. Annual harvests of dolphinfish are estimated at 30,000-40,000 tons. Major exporting countries include Ecuador, Costa Rica, Japan, and the United States. The United States, Japan, Europe, and the Caribbean region are primary consumers of dolphinfish.
